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. 2001 Nov 1;414(6859):43-8.
doi: 10.1038/35102009.

Chemistry of Ion Coordination and Hydration Revealed by a K+ channel-Fab Complex at 2.0 A Resolution

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Chemistry of Ion Coordination and Hydration Revealed by a K+ channel-Fab Complex at 2.0 A Resolution

Y Zhou et al. Nature. .

Abstract

Ion transport proteins must remove an ion's hydration shell to coordinate the ion selectively on the basis of its size and charge. To discover how the K+ channel solves this fundamental aspect of ion conduction, we solved the structure of the KcsA K+ channel in complex with a monoclonal Fab antibody fragment at 2.0 A resolution. Here we show how the K+ channel displaces water molecules around an ion at its extracellular entryway, and how it holds a K+ ion in a square antiprism of water molecules in a cavity near its intracellular entryway. Carbonyl oxygen atoms within the selectivity filter form a very similar square antiprism around each K+ binding site, as if to mimic the waters of hydration. The selectivity filter changes its ion coordination structure in low K+ solutions. This structural change is crucial to the operation of the selectivity filter in the cellular context, where the K+ ion concentration near the selectivity filter varies in response to channel gating.

Comment in

  • See potassium run.
    Miller C. Miller C. Nature. 2001 Nov 1;414(6859):23-4. doi: 10.1038/35102126. Nature. 2001. PMID: 11689922 No abstract available.

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